Carnitine (vitamin Bt; 3-hydroxy-4-trimethylammonio-butanoate) is a quaternary ammonium compound biosynthesized from the amino acids lysine and methionine. Carnitine exists in two stereoisomers. The biologically active form is L-carnitine, whilst its enantiomer, D-carnitine, is biologically inactive. L-carnitine (LC) is an endogenous compound, which plays a key metabolic role, transporting long chain fatty acids into the mitochondria for energetic oxidation. Supplementation with acetyl-L-carnitine (ALC) has been shown to increase overall regional cerebral metabolism in rodents. Carnitine and its esters also have non-metabolic roles in brain function as neuroprotectants, antioxidants and modulators of neurotransmission.
Carnitine deficiencies and chronic fatigue co-exist across a number of patient groups. Early evidence suggests that supplementation may improve indices of chronic fatigue associated with cancer (Cruciani et al. 2006). Evidence also suggests beneficial roles for supplementation with carnitine and its esters in attenuating the symptoms and cognitive deficits associated with Alzheimer's disease (Montgomery et al. 2003) and in reducing fatigue and improving cognitive function in centenarians (Malaguarnera et al., 2007, 2008).
Karlic and Lohninger suggest that carnitine supplementation may foster exercise performance of athletes. They conclude that there is evidence for a beneficial effect of L-carnitine supplementation in training, competition and recovery from strenuous exercise and in regenerative athletics.
JP 2005097161-A discloses an anti-fatigue composition for preventing physical and mental fatigue, which comprises coenzyme Q, carnitine and an inorganic acid as active ingredients.
Another fatigue improver based on biotin, carnitine and pantothenic acid as active ingredients is described in JP 07-233070-A.
A food supplement based on vitamin C, vitamin E, L-carnitine and alpha-lipoic acid for inhibiting the deterioration of cognitive function is disclosed in WO 02/43666 A2.
Therefore, L-carnitine is generally used in the art for the treatment of individuals suffering from diseases, such as cancer or Alzheimer's disease, or having an impaired metabolism as a result of high age or extreme physical exercise. Further, combinations of multiple active agents, comprising L-carnitine, have been suggested for other uses. Compositions for treating fatigue or improving cognitive function described in the art are mixed compositions comprising multiple active ingredients, such as vitamins and antioxidants.